This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-247029 filed on Aug. 16, 2001; the entire contents of this prior application being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a paper bag with a film inner bag, and more particularly to a paper bag that comprises an outer bag element made of paper and an inner bag element as an inner-layer bag made of a synthetic resin film, wherein after the paper bag is filled with a content and stored in or conveyed to a destination, the inner bag element can easily be opened by manual operations after being taken out from the outer bag element or without being taken out from the outer bag element.
2. Description of the Related Art
Conventionally, paper bags having a film inner bag element consisting of a film made of a synthetic resin such as a polyethylene or the like as an inner-layer bag have generally been referred to as xe2x80x9cpaper bags with an inner bag elementxe2x80x9d. Since such bags are suitable in terms of air-tightness, moisture-proof properties and cleanness, these bags have been widely used in large quantities. The conventional paper bags with a film inner bag element are generally configured such that a paper outer bag element consists of two to three layers of craft paper and a film inner bag element consisting of a polyethylene film is provided as the innermost layer of the out bag. The bags have been used for the transportation and storage of foodstuffs such as sugar, various types of powders, cereals, protein, etc., as well as resin pellets or the like (hereafter referred to simply as xe2x80x9ccontentsxe2x80x9d).
Although the conventional paper bags with a film inner bag element have excellent air-tightness, moisture-proof properties and cleanness and therefore are very convenient to use, there is a problem in that it is not easy to open. To describe more specifically on this point, the inner bag element used in the conventional paper bags has a structure in which one end of a tubular body consisting of a synthetic resin film is left open to form a mouth through which contents are filled, while the other end is closed to form a closed bottom part either by heat-sealing across the entire width, by folding two or more times together with the outer bag element or by stitching with a sewing machine together with the outer bag element.
In such a paper bag with a film inner bag element, after it is filled with a specified amount of contents from the open part at one end of the paper bag, i.e., from the mouth part of the inner bag element, the mouth part is closed by heat sealing across the entire width, and finally, the open part at one end of the outer bag element is closed. Thereafter, the paper bag filled with contents is transported or stored, and later the paper bag is opened when it is necessary to take out the contents.
There are two methods of opening the paper bag. In one former method, one end of the outer bag element is cut together with the end portion of the inner bag element inside the outer bag element using scissors or the like so that the paper bag is opened. In another method, the closed parts at both ends of the outer bag element are opened by being undone and the inner bag element is taken out from the outer bag element, and then an end portion of the inner bag element is opened. The former method has a problem in that since the closed end portions of both the outer bag element and the inner bag element, which are securely closed, are opened by being cut with scissors at the same time, an extreme amount of effort is required in order to open the bag, so that the bag cannot be opened quickly.
In the latter method, both ends of the inner bag element that is taken out from the outer bag element remain closed by heat-sealing or the like. Accordingly, one of the end portions of the inner bag element is cut in lateral direction across the entire width or a portion of the width in a position that is located further toward the center of the bag than the heat-sealed portion with respect to the longitudinal direction, thus forming a discharge opening and the contents are removed from this discharge opening.
To make a lateral cut in one end portion of the inner bag element, a tool with a sharp blade such as a cutter knife, scissors or the like has conventionally been used. Thus, in order to remove the contents from the inner bag element that has been filled with the contents and then closed at both ends by heat-sealing, it has always been necessary to using an opening tool such as a blade or the like, both in the former method and latter method described above. In particular, the reason that it is necessary to use a blade or the like even in the latter method is that the synthetic resin films used to form conventional inner bag elements are of the type having properties that prevent tearing by hand.
As a result, to open an inner bag element of this type, it is always necessary to provide an opening tool such as a blade or the like for ready use, which is extremely bothersome. As a result, the working efficiency of the opening process drops considerably. Moreover, when such an opening tool is used to open the inner bag element, it may occur such problem that the worker may accidentally drop the cutter knife, scissors or the like into the opened inner bag element without noticing that, and the contents are sent into a subsequent processing while the contents still contain the dropped opening tool.
Furthermore, when such an opening tool is used to open the inner bag element, there is a possibility that the problem of contamination may occur. Namely, when the end portion of the inner bag element is cut open across, for example, the entire width with scissors or the like, so called xe2x80x9ctwice cuttingxe2x80x9d may easily occur. When the xe2x80x9ctwice cuttingxe2x80x9d occurs, small cut pieces of the inner bag element are produced, and these pieces may be admixed with the contents inside the inner bag element during the opening process.
Further, dust may adhere to the opening tools for opening the paper bag, and it may occur that this dust on the opening tools will fall during use and be admixed with the contents in the inner bag element during the opening process.
Accordingly, there has been a demand for a paper bag with a film inner bag element that can easily be opened, either partially or across the entire width of the bag, by tearing the end portion of the inner bag element in the lateral direction by hand without using a special opening tool, either in cases where the inner bag element is opened after being taken out from the outer bag element, or in cases where the inner bag element is opened without being taken out from the outer bag element.
It is an object of the present invention to provide a paper bag with a film inner bag element which is constructed in order to solve these conventional problems, and which can easily be opened by a manual operation, either partially or across the entire width of the bag, by tearing the end portion of the inner bag element in the lateral direction.
A paper bag with a film inner bag element according to an aspect of the present invention, comprises an outer bag element comprising at least one layer formed mainly from craft paper and having a closed end portion forming a bottom part thereof; and an inner bag element comprising a tubular body formed from a synthetic resin film and having a closed end portion forming a bottom part thereof, the inner bag element being disposed inside the outer bag element, wherein a cut portion used as a tearing guide is formed along the longitudinal direction in an end portion of the inner bag element that is closed by heat-sealing and that is planned to be opened in the future, including the closed end portion on the bottom side, and wherein the synthetic resin film that forms the inner bag element is a thermoplastic resin film having a property of allowing easy tearing in one axial direction, the inner bag element being formed so that the one axial direction is a width direction thereof that is perpendicular to a longitudinal direction thereof.
The paper bag with a film inner bag element according to another aspect of the present invention is characterized in that the paper bag with a film inner bag element is a pleated paper bag which has pleats on both side portions thereof, and wherein the inner bag element has pleated portions in both side portions thereof, and the cut portion is formed with in a position located further toward the center with respect to the width direction than trough-fold positions of the pleated portions when the end portions of the tubular body are placed in a flat state.
The paper bag with a film inner bag element according to still another aspect of the present invention is characterized in that one of a mouth-part closed portion that is closed when the paper bag is closed after the paper bag has been filled with contents and the bottom-part closed portion of the outer bag element, is closed either by stitching with a sewing machine or closed using a covering paper equipped with an opening tape, another of the closed portions is formed so as to constrain the end portion of the inner bag element and never to be opened, and when the contents are to be removed, the outer bag element is opened by tearing the covering paper using the opening tape, or by removing a stitching thread, and then the inner bag element is opened by tearing the heat-sealed end portion of the inner bag element inside the opened outer bag element without taking out the inner bag element from the outer bag element.
The paper bag with a film inner bag element according to further aspect of the present invention is characterized in that both the bottom-part closed part of the outer bag element and a mouth-part closed portion of the outer bag element that is closed when the paper bag is closed after the paper bag has been filled with contents, is closed by folding the end portions of the outer bag element and the end portions of the inner bag element at least one time and by enclosing and fastening these bent portions with covering papers that are equipped with opening tapes, and when the contents are to be removed, both end portions of the outer bag element are opened by tearing the covering papers using the opening tapes, the constraint between the outer bag element and the end portion of the inner bag element is released, the inner bag element is taken out from the outer bag element, and the heat-sealed end portion of the inner bag element is torn so as to open the inner bag element.
The paper bag with a film inner bag element according to still further aspect of the present invention is characterized in that the thermoplastic resin film that forms the inner bag element is made of polyethylene resin or ionomer resin.
Further, the paper bag with a film inner bag element according to an aspect of the present invention is characterized in that the thermoplastic resin film that forms the inner bag element is constituted by a laminated body consisting of a plurality of layers, and at least one of the layers of the laminated body is formed by an ionomer resin layer.
Furthermore, the paper bag with a film inner bag element according to an aspect of the present invention is characterized in that the thermoplastic resin film that forms the inner bag element is a laminated body consisting of three layers in which the ionomer resin layer is disposed as the intermediate layer, and low-density polyethylene resin layers are disposed on both sides of the intermediate layer as the inner layer and outer layer.
Furthermore, the paper bag with a film inner bag element according to an aspect of the present invention is characterized in that the low-density polyethylene resin layers disposed as the inner layer and outer layer are composed of resin film layers in which a low-density polyethylene is blended with a linear low-density polyethylene that is polymerized by a metallocene catalyst in a polyolefin.
Still further, the paper bag with a film inner bag element according to an aspect of the present invention is characterized in that the thermoplastic resin film is at least a stretched film which is stretched only in a direction perpendicular to the one axial direction.